The United States has been sending indirect messages in recent days to the rebel groups that led the offensive to topple Syrian President Bashar al-Assad, officials told The New York Times.

Now that the groups have captured Damascus and succeeded in ousting Assad from power, President Biden and his top advisers are considering the extent to which they should work directly with them in the future, the officials said.

The United States began relaying messages to the rebel groups through the Turkish government, which has ties to them, after they launched their major offensive last week and before capturing the Syrian capital over the weekend, according to American and Turkish officials. One of the officials said the initial messages were intended to tell the groups “what not to do.”

One of the messages the United States sent through the Turkish government was that rebel groups should not allow Islamic State fighters to join their offensive against the Assad government.

The insurgent groups responded through the Turks with assurances that they had no intention of allowing Islamic State to be part of their movement, according to US and Turkish officials briefed on the messages.

The messages have been passed to the Turks through diplomatic, secret and military channels.

In public remarks from the White House on Sunday, Biden said the US would not allow Islamic State to exploit any power vacuum after Assad’s fall.

The broader debate within the Biden administration about more direct contact with the groups centers on their past behavior and connections to extremists.

It also includes ongoing assessments by U.S. intelligence analysts and administration policymakers of whether the groups have, or are willing, to substantially change how the United States and its allies in the region address concerns about their terrorist relationships.

The rebel groups have united under the leadership of Hayat Tahrir al-Sham, or HTS, which the United States has designated a foreign terrorist organization during the Trump administration.

HTS was an offshoot of al-Qaeda, but split off years ago and dominated Syria’s last opposition bastion.

Once considered one of the most powerful extremist factions of the insurgency, the group later sought to shed its radical roots and focused on building a civilian government, albeit an authoritarian and extremist one, in its region.

U.S. intelligence agencies and top Biden administration officials continue to scrutinize HTS and its leader, Abu Mohammed al-Jolani, who now appears moderate, allaying concerns about their intentions and past relationships.

US officials said the Biden administration is allowed to talk with HTS and its leader, even though they are on the terrorist list, but the administration cannot provide them with material support.

While the Biden administration has so far not stopped talking directly to HTS, it is working closely and directly with the US military’s main partner in Syria, the Kurdish militia, the Syrian Democratic Forces, or SDF.

According to US officials, the government encouraged and provided intelligence support to the SDF for operations to control Syrian territory in eastern Syria, including the cities of Deir al-Zour and Abu Kamal. .

The officials said the operations were intended to ensure that Islamic State could not take advantage of the situation and seize the areas as Syrian government forces withdrew.

According to a US official, the message the United States sent to the SDF was: “If the regime withdraws from territory, it will go to someone, so you should fill the gap yourself instead of letting ISIS do it.”